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Патент USA US2127907

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Patented Aug. 23, 1938
Peter Fireman, Lambertville, N. J., assignor to
Magnetic Pigment Company, New York, N. Y.,
a corporation, of New York
No Drawing. Application March 20, 1937,
_Serial No. 132,099
2 Claims.
(01. 23-200)
This invention relates to the production of iron
compounds adapted especially for use as pigments
and for other purposes.
In Patents Nos. 1,327,061 and 1,368,748, Penni
man and Zoph have described a process of pro
ducing iron compounds which has been used com
mercially for many years. Brie?y, the process
comprises the addition of a colloidal hydrate of
iron, precipitated from a solution of an iron salt,
10 to a water solution of an iron salt, and oxidation
in the presence of metallic iron by the introduc
tion of an oxidizing agent such as air with steam
in quantity su?lcient to maintain a preferred tem
perature of about 60° C. It has been the practice
in the commercial use of the Penniman and Zoph
process to avoid any temperature exceeding sub
stantially that speci?ed by the patentees. Higher
temperatures were believed to be detrimental to
the product and to involve such a waste of steam
20 as to be commercially impracticable because the
proportion of steam required increases rapidly
with each degree of temperature rise obtained,
particularly while a steady and copious current
of air is passing through the solution.
It is the object of the present invention to pro
vide an improved process of producing iron com
pounds and products thereof which have more
desirable characteristics.
Other objects and advantages of the invention
30 will be apparent as it is better understood by
reference to the following speci?cation, in which
I have described the preferred procedure for the
accomplishment of the intended purpose.
I have discovered that, contrary to expectation,
35 the oxidation of solutions of iron compounds in
the presence of metallic iron can be conducted
more effectively at temperatures at or close to the
boiling point and preferably at or about 90° to 95°
Such relatively high temperatures, as com
pared with the temperatures commonly employed
in the Penniman and Zoph process, require a
supply of steam greatly exceeding that necessary
to maintain a temperature of, for example, 60° C.
However, the acceleration of the reaction and the
improved characteristics of the product are such
as to fully warrant the additional expenditure for
the steam supply.
In carrying out the invention, it is necessary to
modify the equipment used heretofore in the
Penniman and Zoph process to afford a sufficient
outlet for the much greater volume of steam and
air which escapes from the solution during the
operation. This, of course, involves losses of heat
supplied in the form of steam. Additional losses
occur because of the greater volume of air which
is introduced simultaneously for the purpose of
oxidation and the corresponding accelerated dis
charge of the unused portion of the air. How
ever, as indicated, I have found it more economi~
cal and otherwise desirable to conduct the opera- 5
tion at the higher temperatures indicated.
Inaddition to the improvement effected in the
procedure, the products obtained are superior to
those produced by the Penniman and Zoph proc
The latter affords a product which is ochre
ous yellow, varying in depth of color from light
(lemon) yellow, through a medium (orange)
yellow, to a deep (dark orange) yellow. The vari
ation in shade depends upon the length of time——
number of days-during which the operation con 15
tinues. As the result of the operation herein
described, the products have lighter shades and
are clearer yellows, less brownish in appearance
in oil, stronger in undertone (when reduced with
white) and the undertone is more greenish-yellow
in contrast to the reddish characteristic of the
product obtained at lower temperatures. More
over, the red pigments resulting from the calci
nation of yellow pigments produced in accordance
with the present invention are brighter and
I am, therefore, able to- produce a more
acceptable product having numerous advantages
in its commercial applications. The product is
ferric oxide monohydrate having one molecule of
chemically combined Water (FezO3.HzO) and usu
ally has in addition approximately two percent
(2%) of adsorbed water.
In carrying out the invention, I prepare a col
loidal precipitate or nucleus of ferric hydrate,
preferably by the addition of a suitable alkaline
agent, such as caustic soda or potash, to a solution
of a soluble ferric salt. Of the available alkali
and alkaline earth precipitating agents which
might be used, caustic soda produces pigments of
the highest quality.
A soluble ferrous salt may be 40
precipitated similarly, and the precipitate may be
oxidized by the introduction of air to the ferric
form. The colloidal ferric hydrate is then mixed
in the same or in a separate receptacle with a
solution of an iron salt. Metallic iron is immersed
in the solution, and steam is introduced at a rate
su?icient to raise the temperature to, and to
maintain it at or about, 90° to 95° C., while an
oxidizing agent such as air is simultaneously
introduced in order to effect the oxidation and 50
precipitation of the desired pigment material.
Oxidation and reduction by the metallic iron
occur continuously in the solution in a cyclic
manner, and the continued operation results in
the formation of a pigment which in the earlier 55
stages is a light shade of yellow, changing through
the continued operation of the process to darker
shades of yellow. The process is continued until
the desired shade is attained. Introduction of
the colloidal ferric hydrate in the initial stage of
the process prevents the formation of crystalline
products which reduce the value and e?fectiveness
of the material for pigment purposes.
The proportions employed in the practice of the
10 invention may vary widely. It is desirable to
employ the nuclear material in the proportion of
about 10 to 50 pounds to each 1000 gallons of the
solution. This, however, is merely an example of
good commercial practice. The proportions are
15 not critical, and can be increased or reduced very
Various changes may be made in the procedure
and particularly in details of operation without
departing from the invention or sacri?cing the
advantages thereof.
I claim:
1. The method of preparing an hydrated oxide
of iron suitable for pigments which comprises
immersing metallic iron in a solution of an iron
salt, heating and maintaining the temperature of
the solution at approximately 90° to 95° C., and 10
simultaneously supplying a gas containing free
oxygen to the solution.
2. The method of preparing an hydrated oxide
of iron suitable for pigments which comprises
immersing metallic iron in a solution of an iron
considerably without substantial modi?cation of salt containing a precipitated iron hydrate, heat
the results.
ing and maintaining the temperature of the solu
The invention and its advantages depend upon tion at approximately 90° to 95° C., and simul
operation at a temperature at or about the boiling
point of the solution. I have found that tempera
tures at or about 90° to 95° C. produce the best
results, but the invention is not limited to the
speci?c range indicated.
taneously supplying a gas containing free oxygen
to the solution.
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